Such a high voltage swivel is known from U.S. Pat. No. 7,137,822 in the name of the applicant. The known swivel is a high voltage swivel for offshore applications, for instance for distributing electrical power, that is generated on a weathervaning Floating Production, Storage and Offloading vessel (FPSO)—which FPSO is anchored to the sea bed via a turret—to a sub sea power cable. Geostationary hydrocarbon risers extend upwards from a well head to a power plant on the vessel, in which the hydrocarbons are converted into electrical energy. The electrical connection of the rotating vessel to the stationary sub sea power cable leading to shore is achieved by the high voltage swivel in which the stator is connected, via the geostationary swivel part on the vessel, to the sub sea power cable and the rotor is connected to the power plant on the vessel.
The conductors of the inner and outer bodies of the known high voltage swivel are embedded in solid annular insulator rings which fully surround the conductors, apart from their contact areas. This results in a very good electrical insulation and the use of a solid insulator in stead of air or a dielectric oil allows a compact design and operation at relatively high voltages. The conductors comprise concentric rings each having an annular metal contact surface via which the inner and outer conductors make full contact, such that the mechanical forces and electrodynamic forces as well as the currents are distributed evenly over the full circumference.
The known swivel has the disadvantage that there is a risk of short circuits after the system has been in operational use for a while and the conductors start to show some wear. When debris originating from wear get in the narrow space between the conductors and the insulating rings, short circuits can be created, causing the swivel to malfunction. Upon wear of the spring elements at the contact surfaces of the annular conductors, the solid insulator rings and conductors of the swivel need to be dismantled in order to obtain access to the electrodes.
It therefore is an object of the invention to reduce the risk of malfunctioning of the swivel due to debris. It is a further object of the invention to reduce the amount of wear of the conductors and the amount of debris, while obtaining a good electrical contact. It is again an object of the invention to provide a swivel of reduced weight, in which the inner and outer annular conductors are accurately aligned and can take up large mechanical and electrodynamic loads, especially under offshore conditions. The swivel should allow easy handling during assembly and disassembly for inspection or replacement purposes.